'use strict';

function median_to_letter(collection) {

  //在这里写入代码
  var median_sum = 0
  if(collection.length%2==0){
    median_sum = Math.ceil((collection[collection.length/2]+collection[collection.length/2+1])/2)
  }
  else {
    median_sum = collection[(collection.length+1)/2]
  }
  var num1 = String.fromCharCode(97+median_sum/26-1)
  var num2 = String.fromCharCode(97+median_sum%26-2)
  return num1+num2;
}

module.exports = median_to_letter;
